1. Field of the Invention
This invention relates to a dense substrate for a solid oxide fuel cell (which will hereinafter be referred to as SOFC) in which an electrochemical reaction is carried out to take out electric energy, a solid oxide fuel cell using the same substrate, and a method of manufacturing the same solid oxide fuel cell.
2. Description of the Prior Art
There are known SOFC's which include a tubular SOFC (Japanese Patent Laid-Open No. 73246/1979) formed by providing a plurality of single cells, each of which consists of a fuel electrode, electrolyte and an air electrode, on the outer surface of an elongated cylindrical porous support tube, and connecting the single cells in series, and a monolithic SOFC (Japanese Patent Laid-Open No. 100376/1985) formed by sandwiching a flat cell section, which consists of three layers of a fuel electrode, an electrolyte and an air electrode, between corrugated mutual-connection walls each of which consists of three layers of an air electrode, an interconnection and a fuel electrode.
Regarding the practical use of SOFC's, a tubular SOFC can be manufactured comparatively easily but a support tube cannot be made extremely thin in view of the structure thereof. Therefore, this type-of SOFC does not have as high of an output performance per volume. A monolithic SOFC has a high output performance per volume but involves very difficult manufacturing problems in the production of a cell, a gas sealing, assembling, etc. The inventors of the present invention then filed a patent application, i.e. Japanese Patent Application No. 106610/1990, which has been laid-open to public inspection under Laid-Open No. 6752/1992, for the solid oxide fuel cell disclosed therein, so as to solve these problems. According to this invention, the portion of a dense substrate to which a cell section is to be fixed is subjected to a mechanical boring process. Carrying out this process is difficult, and presents a problem concerning the dimensional accuracy thereof.
Moreover, in a conventional method of this kind, a plurality of cell sections are manufactured simultaneously or assembled unitarily at a time. Consequently, when a failure occurs in one cell section, there is the possibility that the whole assembly cell stacks or cell sections become unusable.